Gelo’s unique interface streamlines the coloring process. You’re able to work with a wide variety of solid colors to enhance tones by sliding your finger across the wheel. Gradients can also be applied to give your photos a more moody look. Three different shape tools are available as well, allowing you to apply color to specific areas.

Geló | Add color with gels, shapes and gradients is available for free for a limited time. It has a 4-star rating with a total of 22 ratings.

PolyPic ($1.99 → Free, 692.6 KB): Create abstract compositions out of your own photos with PolyPic. It’s for photographers with an artistic eye.

You’re able to import any photo from your library or take a new one from within the app. You’re then able to apply one of the 19 polygon effects along with one of the 19 filters. You’re also able to switch between large and small polygons. When your work of art is complete, share it via email, Facebook, Instagram, or Twitter.

PolyPic is available for free for a limited time. It has a 4-star rating with a total of 29 ratings.

Universal:

Dangerous monsters are threatening life across the entire universe. It’s up to you to craft your own personal spaceship and join Space Jack’s quest to save the universe. You’re able to control your ship’s horizontal movements via tilt or touch. Your ship will automatically fire upon your approaching enemies, but you can quickly dodge their fire with a swipe. Your fallen enemies will drop Qubes, which you must collect in order to craft your own ship from scratch. Ship designs can be shared with other players, and you can even 3-D print your creations with a single tap.

Space Qube® is available for free today only (06/07). It has a 4-star rating with a total of 1076 ratings.

Wind Tunnel is a fun distraction for those with curious minds. As wind goes speeding down a tunnel, you’re able to directly interact with particles and smoke or draw obstacles. The app includes a wide variety of customization settings, including the ability to adjust physical parameters like fluid viscosity, obstacle friction, and wind speed. The app also includes tons of predefined scenes to interact with, the ability to save and load your own scenes, and a free space mode where you create your own wind.

Wind Tunnel Pro HD is available for free for a limited time. It has a 4.5-star rating with a total of 41 ratings.

iPad:

Flick Tennis HD ($4.99 → Free, 142.2 MB): Play as a tennis prodigy fighting to become the best college player in Flick Tennis HD. It’s for fans of sports games.

Make your way through the 11 episodes in story mode by defeating the most challenging of opponents. Swipe up and down with one or two fingers to perform different shots, and simply tap where you want your character to go after your shot. The game also includes exhibition and multiplayer modes, 35 comic book pages in story mode, 12 difficulty variations, 11 courts, and 10 players to choose from.

Flick Tennis HD is available for free for a limited time. It has a 4-star rating with a total of 103 ratings.

That concludes today’s issue of Apps Gone Free. If you like staying on top of these daily deals, don’t forget to check out our free AppsGoneFree app. It provides all the deals each day, and even an archive of past deals that are still active.

Developers:

If you are a developer who would like to get your app included in our “Apps Gone Free” daily lists, here’s our basic set of rules:

It must have at least a three-star average rating at the time it goes free.

The app must not have been free numerous times (3+) over the last six months.

The free version of your app must not include ads.

To submit an app, simply send a request to [email protected] with the subject “Apps Gone Free.” Please include the name of the app, a link to it in the App Store, when and for how long you intend to offer the app for free, and anything else you would like to share. We will take it from there.